WASHINGTON (CNN) -- A top GOP senator Wednesday warned that Michael Mukasey's nomination for attorney general is "at risk" because the retired federal judge refused to categorically declare that a controversial interrogation technique is torture.

A senior Democratic senator predicted Wednesday that Michael Mukasey would be confirmed.

However, a senior Democratic senator on the Senate Judiciary Committee told CNN on Wednesday that Mukasey probably will win approval from the committee and the full Senate.

"My guess is he does," get approved by the committee, said the senator, who asked not to be quoted by name.

"If he gets through the committee, it's almost assured" he'll be approved by the full Senate.

In answers to questions from the Senate Judiciary Committee about the use of waterboarding against suspected terrorists, Mukasey told senators he found the practice "repugnant."

"I think we need to have a very frank discussion with more facts available," said Sen. Arlen Specter of Pennsylvania, the committee's ranking Republican, who warned that the nomination was at risk. "And I believe that can only be done in a closed-door session. I would hope we might do that early next week."

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The committee's chairman, Vermont Democrat Patrick Leahy, has scheduled a Tuesday meeting to take up Mukasey's nomination.

"Obviously, many of us felt that the United States -- which would roundly and universally condemn the waterboarding of an American held by any other country -- many of us had felt that the attorney general nominee should do the same thing," Leahy said.

While the nine Republicans on the Judiciary Committee appeared to favor Mukasey, there are still questions about how many of the 10 Democrats on the committee will vote for him. It would take only one Democrat to side with all the Republicans for Mukasey to win committee approval.

But other key Democrats -- Sens. Dianne Feinstein of California, Russ Feingold of Wisconsin and Ben Cardin of Maryland -- said they have concerns about the waterboarding issue, but think Mukasey is strong in other areas and aren't ready to close the door on his nomination.

Leahy said he is close to making up his mind on which way to vote but will take the weekend to decide.

The White House expressed confidence in President Bush's pick for attorney general despite senators' concerns about his views on waterboarding as well as his answers about the president's power to order electronic surveillance without a warrant.

"We feel confident that he will be confirmed," White House spokeswoman Dana Perino told reporters.

In further written statements released Wednesday, Mukasey said the president is bound to follow the Foreign Intelligence Surveillance Act, which requires a special federal court to approve wiretaps on people inside the United States. But he said that while FISA remains the foundation for foreign intelligence-gathering, arguments that the president's constitutional power as commander-in-chief of the armed forces supersedes the law could pose "a difficult separation of powers question."

The Bush administration argued the president's authority as commander-in-chief allowed him to order the National Security Agency to monitor communications between people in the United States and those overseas suspected of having ties to terrorists. The program, disclosed in 2005, was launched without following FISA, which was passed in response to Watergate-era wiretapping abuses.

Mukasey's written answers to the committee repeated the positions he took in his October 18 confirmation hearing, when he told senators he has not received classified briefings on what techniques American interrogators are allowed to use on suspected terrorists and can't make a legal judgment.

Sources with knowledge of the CIA-run interrogation program have said waterboarding is not being used as part of its interrogations now. But those sources have said waterboarding was used in the interrogation of Khalid Shaikh Mohammed, now facing trial for planning al Qaeda's 2001 attacks on New York and Washington.

The practice -- in which interrogators produce the sensation of drowning in a restrained prisoner by either dunking him in water or pouring water over his face -- was used by the Spanish Inquisition, Cambodia's Khmer Rouge and the World War II Japanese military, according to Human Rights Watch.

It was specifically banned in U.S. law governing the treatment of prisoners by the U.S. military.

Bush has admitted authorizing the use of "alternative" interrogation techniques against suspected terrorists, though his administration insists it does not torture prisoners.

White House Counselor Ed Gillespie said Mukasey can't get classified briefings until he's confirmed -- but he said senators who have been told details of the CIA's top-secret "enhanced interrogation" program have declared it legal.

"The fact is the government doesn't confirm techniques regardless of whether they're used or not used," Gillespie said. "They don't rule in or out, because the idea is not to help terrorists who would mean to do us harm know what to train or not train for."

Mukasey has been nominated to replace Alberto Gonzales, who resigned in September amid multiple controversies stemming from his stewardship of the Justice Department.

In 2002, while serving as White House counsel, Gonzales wrote that terrorists captured overseas should not be covered by the Geneva Conventions and that the battle against the al Qaeda terrorist network "renders obsolete Geneva's strict limitations on questioning of enemy prisoners and renders quaint some of its provisions."

When the memo became public after the Abu Ghraib scandal broke in 2004, Gonzales said the measure did not give U.S. officials a green light to torture or abuse prisoners.

After his departure, The New York Times reported that Justice Department memos written during his tenure endorsed "the harshest interrogation techniques ever used" by the CIA. Democrats accused the administration of secretly reversing its public 2004 disavowal of the use of torture, but the White House said the documents were consistent with that pledge.

Gonzales was also accused of misleading Congress about the NSA surveillance program during testimony after its disclosure.E-mail to a friend